Related-art air-conditioning apparatuses, used as building multi-air-conditioning apparatuses, include an air-conditioning apparatus in which an intermediate heat exchanger is allowed to exchange heat between a refrigerant heated or cooled on a heat source side and a heat medium flowing through a use side circuit such that heat energy produced on the heat source side is transmitted to a use side heat exchanger (i.e., an indoor unit) (refer to Patent Literature 1, for example). The air-conditioning apparatus disclosed in Patent Literature 1 detects the difference in temperature (hereinafter, referred to as the “indoor-unit inlet-outlet temperature difference”) between the heat medium flowing into the use side heat exchanger and that flowing out of the use side heat exchanger. This air-conditioning apparatus is configured such that, when the indoor-unit inlet-outlet temperature difference is less than a control target value, the area of opening of a flow control valve is reduced to reduce the flow rate of the heat medium flowing through the use side heat exchanger, and when the temperature difference is greater than the control target value, the area of opening of the flow control valve is increased to increase the flow rate of the heat medium flowing through the use side heat exchanger, such that the indoor-unit inlet-outlet temperature difference approaches the control target value. Accordingly, the heat medium is supplied according to a heat load on the use side heat exchanger. Patent Literature 1 further discloses an arrangement in which a plurality of intermediate heat exchangers (described as “intermediate heat exchangers” in Patent Literature 1) are connected to a refrigeration cycle on the heat source side.
Patent Literature 2 discloses another related-art air-conditioning apparatus in which an intermediate heat exchanger is allowed to exchange heat between a refrigerant heated or cooled on a heat source side and a heat medium flowing through a use side circuit such that heat energy produced on the heat source side is transmitted to a use side heat exchanger (i.e., an indoor unit). The air-conditioning apparatus (referred to as a “heat pump system” in Patent Literature 2) disclosed in Patent Literature 2 controls the circulation rate of the refrigerant on the basis of a first target temperature which is the temperature of the heat medium (referred to as an “aqueous medium” in Patent Literature 1) at an outlet of the intermediate heat exchanger (referred to as a “use side heat exchanger” in Patent Literature 1) and controls the operating capacity of a circulation pump for circulating the heat medium such that the temperature difference between the heat medium flowing into the intermediate heat exchanger and that flowing out of the intermediate heat exchanger reaches a second target temperature difference. In the air-conditioning apparatus disclosed in Patent Literature 2, when the temperature difference between the heat medium flowing into the intermediate heat exchanger and that flowing out of the intermediate heat exchanger is less than the second target temperature difference and the temperature of the heat medium at the outlet of the intermediate heat exchanger is higher than or equal to the first target temperature, the operating capacity of the circulation pump is reduced. On the other hand, when the temperature difference between the heat medium flowing into the intermediate heat exchanger and that flowing out of the intermediate heat exchanger is greater than the second target temperature difference, the operating capacity of the circulation pump is increased. Furthermore, Patent Literature 2 discloses an arrangement in which a plurality of intermediate heat exchangers are connected in parallel with a refrigeration cycle on the heat source side.